Coaxial planetary converters include an input shaft, which usually is the high speed shaft. Eccentrics are fixed on the input shaft, and carry bearings on which planet wheels are mounted. The planet wheels in turn mesh with a ring gear carried by a fixed housing, and with a ring gear carried by the output shaft.
Conventional torque converters are encumbered with two major problems, one being that strong radial loads are produced at the contact point of the eccentrics with their associated ring gears, which must be absorbed by the support bearings of the input and output shafts. Another problem is that the rotation of eccentric masses produces strong vibrations.